Neutrophil activation and chemotaxis have recently acquired increased attention through the discovery of the potent neutrophil activating peptide 1/interleukin-8 (IL-8), Walz, A. et al., Biochem. Biophys. Res. Commun. 149:755 (1987), Schroder, J. M. et al., Immunol. 139:3474 (1987), Yoshimura, T. et al., Proc. Natl. Acad. Sci. U.S.A. 84:9233 (1987) and Baggiolini, M. et al., J. Clin. Invest. 84:1045 (1989). Subsequently, two structural homologues with similar biological activities on human neutrophils were detected, neutrophil-activating peptide 2 (NAP-2), which is formed by proteolytic processing from platelet basic protein (PBP) or connective-tissue activating peptide III (CTAP-III) released from platelet .alpha.-granules, Walz, A. and M. Baggiolini, Biochem. Biophys. Res. Commun. 159:969 (1989) and Walz, A. and M. Baggiolini, J. Exp. Med. 171:449 (1990), and GRO.alpha., which was originally described as a mitogen for human melanoma cells, Richmond, A. et al., EMBO J. 7:2025 (1988) and was subsequently shown to activate neutrophils, Moser, B. et al., J. Exp. Med. 171:1797 (1990) and Schroder, J. -M. et al., J. Exp. Med. 171:1091 (1990). IL-8, NAP-2 and GRO.alpha. belong to a family of peptides with a molecular weight of 8-10 kD, containing four conserved cysteine residues, the first two spaced by one amino acid (CXC). Two other members of this family are platelet factor 4 (PF-4) and .gamma.-interferon inducible peptide 10 (.gamma.IP-10) Deuel, T. F. et al., Proc. Natl. Acad. Sci. U.S.A. 74:2256 (1977) and Luster, A. D. and J. V. Ravetch, J. Exp. Med. 166:1084 (1987).
Whereas the formation of NAP-2 is probably limited to the vascular system, IL-8 and GRO.alpha. were shown to be secreted by a wide variety of cells. This and the demonstration of their in vivo chemotactic activity strongly supports their involvement in a number of inflammatory processes through the triggering of neutrophil infiltration and activation.
Neutrophil infiltration into the alveolar space is prominent in a variety of acute and chronic pulmonary inflammatory disorders. Alveolar macrophages, Rankin, J. A. et al., J. Clin. Invest. 86:1556 (1990) and Strieter, R. M. et al., Am. J. Respir. Cell Mol. Biol. 2:321 (1990) as well as lung epithelial cells, Standiford, T. J. et al., J. Clin. Invest. 86:1945 (1990) and fibroblasts, Golds, E. E. et al., Biochem. J. 259:585 (1989) have been shown to produce IL-8 in response to stimulation. IL-8 is also released by endothelial cells, which, like macrophages respond to LPS in addition to IL-1 and TNF.alpha., Strieter, R. M. et al., Science 243:1467 (1989). Lung fibroblasts were shown to produce GRO.alpha. in addition to IL-8 when stimulated with inflammatory cytokines, Golds, E. E. et al., Biochem. J. 259:585 (1989).
Since the pulmonary alveolus is in direct contact with the external environment, the alveolar macrophage might be the primary target of exogenous stimuli, such as viruses or bacterial products, which induce the expression of proinflammatory cytokines such as IL-1 and TNF.alpha..
Type II alveolar cells appear to have a prominent role in the generation of neutrophil attractants. Here we describe the isolation and complete primary structure of a novel neutrophil activating peptide (ENA-78) from the human type II epithelial cell line A549.